Class V Underground Injection Control Study

The Class V Underground Injection Control Study is a comprehensive look nationwide at 22 types of Class V wells. The 23-volume study (EPA/816-R- 99-014, September 1999) summarizes the occurrence and numbers of Class V wells of each type. It also covers what is being injected into these wells and how states regulate them.

The study was required under a 1997 consent decree with the Sierra Club (Sierra Club v. Browner, D.D.C., Civil Action No. 93-2644 NHJ). The consent decree required EPA to evaluate the risk to underground sources of drinking water (USDWs) associated with Class V wells. EPA was also required to determine whether existing federal UIC regulations were adequate to prevent these wells from endangering USDWs, whether additional federal regulations for any of the well types were warranted and, if so, how each well type should be regulated.

The study describes the types of Class V wells except motor vehicle waste disposal wells and large-capacity cesspools. Motor vehicle waste disposal wells and large-capacity cesspools are the Class V wells that pose the highest risk to USDWs. They are addressed by the Class V Rule.

On June 7, 2002, EPA published in the Federal Register its Final Determination that existing federal UIC regulations were adequate to prevent Class V wells from endangering USDWs and additional federal requirements were not needed. The Final Determination was based on the study and on other available information.

The products of the study include fact sheets on each well type and 23 volumes that address each well type. These are available at the links below.

Volume 3: Storm Water Drainage Wells (PDF)(99 pp, 1.4MB) are shallow injection wells designed for the disposal of rain water and melted snow. These wells typically drain paved areas such as streets and parking lots as well as roofs. Improved sinkholes and abandoned drinking water wells that receive storm water runoff are considered storm water drainage wells.

Volume 4: Carwashes Without Undercarriage Washing or Engine Cleaning (PDF)(48 pp, 1.8MB) use Class V wells to dispose of washwater. These facilities wash only the exterior of vehicles. (They sometimes are called “wand washes.”) This category includes wells that receive used washwater at facilities designed for washing all kinds of vehicles: cars, vans, trucks, buses, boats on trailers, etc.

Volume 5: Large-Capacity Septic Systems (PDF)(123 pp, 2.5MB) dispose of sanitary waste through a septic tank and are used by multiple dwellings, business establishments, communities, and regional business establishments for the injection of wastes. Systems serving single families and non-residential systems serving less than 20 persons are not included.

Volume 6: Food Processing Disposal Wells (PDF)(72 pp, 1.6MB) receive wastewater related to the preparation of food and water used to wash food-processing equipment or facilities. These wells are usually constructed as septic tanks and leachfields, although some are simply drywells that allow untreated wastewater to enter the soil.

Volume 7: Sewage Treatment Effluent Wells (PDF)(127 pp, 1.9MB) are used by privately or publicly owned treatment works (POTWs) to inject treated or untreated domestic sewage through a vertical well or a leachfield. Aquifer recharge wells, aquifer storage and recovery wells, subsidence control wells, and saline intrusion barrier wells injecting treated or untreated wastewater are considered sewage treatment effluent wells for the purposes of this study.

Volume 9: Spent Brine Return Flow Wells (PDF)(29 pp, 670K) dispose of the spent brine that results from the extraction of minerals, halogens, and other compounds from fluids. These wells are commonly associated with manufacturing facilities that produce specialty chemicals such as boron, bromine, magnesia, or their derivatives.

Volume 10: Mine Backfill Wells (PDF)(74 pp, 2.2MB) inject water, sand, mill tailings, or other mining byproducts in order to control subsidence caused by mining, to dispose of mining byproducts, or to fill sections of a mine.

Volume 12: Solution Mining Wells (PDF)(23 pp, 334K) inject leaching solutions (lixiviants) to remove mineral ores from their original geological settings. The saturated solution is extracted by a production well, and the target mineral is harvested for processing. This process is used to mine copper, gold, salt, silver, and uranium.

Volume 15: Experimental Wells (PDF)(53 pp, 621K) are used to test new technologies. Wells will not be classified as experimental if the technology can be considered under an established well subclass. For example, a well used for bioremediation will be classified as an aquifer remediation well.

Volume 16: Aquifer Remediation Wells (PDF)(83 pp, 1.3MB) are used to clean up, treat, or prevent contamination of underground sources of drinking water (USDWs). Treated ground water (pump and treat), bioremediation agents, or other recovery enhancement materials may be injected into the subsurface via Class V wells. These wells may be associated with Resource Conservation and Recovery Act (RCRA) or Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) projects.

Volume 19: Heat Pump/Air Conditioning Return Flow Wells (PDF)(62 pp, 1.2MB) reinject ground water that has been passed through a heat exchanger to heat or cool buildings. A heat pump takes thermal energy from the ground water and transfers it to the space being heated. When cooling is required, the heat pump removes heat from a building and transfers it to the ground water.

Volume 21: Aquifer Recharge/Recovery Wells (PDF)(73 pp, 1.4MB) are used to inject fluids to recharge an aquifer. These wells may have secondary purposes such as saline intrusion prevention, subsidence control, or aquifer storage and recovery (ASR).

Volume 23: Subsidence Control Wells (PDF)(18 pp, 227K) are used to control land subsidence caused by ground water withdrawal or over pumping of oil and gas. These wells may have secondary purposes such as aquifer recharge.